There were some important improvements to the RGB to HAM8 conversion algorithm. Pictures produced by the new version have less artefacts and are more detailed.
- Colorspace conversion algorithm is now much more precise. Earlier version was crude and resulted in some nasty artefacts. For example choosing SET colour from 6-bit RGB base palette (just 4 shades per component!) was almost always choosing darker shade. It was a temporary hack to eliminate some other artefacts. The new method is still not perfect. If the picked colour is lighter than the original it sometimes produces a few much too light pixels.
- Error calculation used to choose operation (SET, Modify Red, Modify Green, Modify Blue) is modified to use weighted sum based on sensitivity of the human eye to each of the primary colours: 2*error_red+3*error_green+1*error_blue. A human eye has the highest sensitivity to green and the lowest to blue. It also eliminated much of the artefacts at the edges of the each object. Most of the ugly areas of more of less random colours at the edges are now just a mild blue-violet glows which are much less noticeable. There were also some less important bugs in this algorithm.
Update (8.11.2013): final version is ready.
Just a small update: weighted error calculation was made optional. This new method improves detail preservation but there are a few situations where the older one causes less disturbing artefacts like trees with a blue sky in the back or small blue details.
Newer versions can be found here.
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